America has recently been confronted with a new and potentially disastrous substance called "ice." This smokable form of methamphetamine has already become the leading drug problem in Hawaii. Accompanying the concern over ice has been the reemergence of methamphetamine as a popular substance of abuse in many parts of the nation. While media and research attention has largely focused on cocaine, sharp increases in drug problem indicators (criminal justice, treatment admissions, emergency room mentions) all suggest that methamphetamine could reach the epidemic proportions now seen with crack. The proposed study will provide a basis for scientific inquiry into the growing and shifting problem of methamphetamine abuse in general and the phenomenon of "ice" in particular. This research will examine a range of urgent and unexplored issues involving this substance among a non-clinical population of moderate to heavy methamphetamine users. To accomplish this goal, we intend to locate and interview 450 current users in three cities experiencing the greatest problems related to different forms of methamphetamine use: Honolulu, San Diego, and the San Francisco Bay Area. This will allow us to 1) uncover and examine the rationale, context, and patterns of methamphetamine use among a non-clinical sample of users; 2) chart the pattern of diffusion of methamphetamine use among our target populations accounting for both static and shifting patterns, motives, modes, amount and frequency of use; 3) correlate differences in the amount, frequency, patterns, motives, and modes of use with specific target populations in our study sites; 4) examine the external and internal constraints which limit use, or modes of use, within all target populations, and compare and contrast these constraints across a range of characteristics (user group, age, occupation, ethnicity, other drug use); 5) examine the relationship between various characteristics of use on a range of consequences (mental and physical health, economic, employment, social, and criminal problems); and 6) generate conceptual frameworks regarding the context and diffusion of methamphetamine use, characteristics of abuse, and potential influence on the overall drug problem in the United States.